Dual culture of the oomycete Lagenisma coscinodisci Drebes and Coscinodiscus diatoms as a model for plankton/parasite interactions

Abstract

Diatoms are thought to provide about 40% of total global photosynthesis and diatoms of the genus Coscinodiscus are an important, sometimes dominant, cosmopolitan component of the marine diatom community. The oomycete parasitoid Lagenisma coscinodisci is widespread in the northern hemisphere on its hosts in the genus Coscinodiscus. Because of its potential ecological importance, it would be a suitable pathogen model to investigate plankton/parasite interactions, but the species cannot be cultivated on media without its host, so far. Thus, it was the aim of this study to explore the potential of dual culture of host and pathogen in the laboratory and to optimise cultivation to ensure a long-term cultivation of the pathogen. Here, we report successful cultivation of a single spore strain of L. coscinodisci (Isla), on several Coscinodiscus species and strains, as well as the establishment of a cultivation routine with Coscinodiscus granii (CGS1 and CG36), which enabled us to maintain the single spore strain for more than 3 years in 6 cm Petri dishes and 10 ml tissue culture flasks. This opens up the opportunity to study the processes and mechanism in plankton/parasitoid interactions under controlled conditions.

Phylogeny and cultivation of the holocarpic oomycete Diatomophthora perforans comb. nov., an endoparasitoid of marine diatoms

“…Cultivation was done in a climate chamber (Conviron, CMP 6010, Canada) at 16°C and 12°C, for 14 h and 10 h, respectively, cycle program with 18 μM/ (sm 2 ) at the 14-h lighting period (Narva, bio-vital, Germany) in 9-cm petri dishes (Sarstedt, Nümbrecht, Germany). Serial sub-culturing procedures for achieving pure cultures were performed as described previously by Buaya et al (2019c). Once a week, four infected diatoms containing a single parasite thallus were inoculated into healthy 2-week-old cultures of P. intermedium and 1-week-old cultures of C. concinnus, to maintain the cultures.…”

“…Miracula helgolandica was inferred to Section Editor: Marc Stadler be the earliest-diverging oomycete lineage together with the recently described freshwater parasitoid M. moenusica, while D. drebesii formed a monophyletic group together with D. gillii and uncultured environmental sequences (Buaya and Thines 2019;Buaya et al 2017;2019a). Only recently, phylogenetic affinities of the genus Olpidiopsis and Ectrogella were resolved and their type species epitypified, leading to the taxonomic revisions of these two important taxa of early-diverging oomycetes (Buaya et al 2019c; Buaya and Thines 2020). The genus Olpidiopsis with its type species O. saprolegniae was found to be unrelated to the parasites of red algae and diatoms parasitoids (Buaya et al 2019c).…”

“…Only recently, phylogenetic affinities of the genus Olpidiopsis and Ectrogella were resolved and their type species epitypified, leading to the taxonomic revisions of these two important taxa of early-diverging oomycetes (Buaya et al 2019c; Buaya and Thines 2020). The genus Olpidiopsis with its type species O. saprolegniae was found to be unrelated to the parasites of red algae and diatoms parasitoids (Buaya et al 2019c). Even though monophyly of the parasites of red algae was not resolved in Badis et al 2019, a monophyletic grouping was observed in Buaya et al (2019c) and Buaya and Thines (2020).…”

“…The genus Olpidiopsis with its type species O. saprolegniae was found to be unrelated to the parasites of red algae and diatoms parasitoids (Buaya et al 2019c). Even though monophyly of the parasites of red algae was not resolved in Badis et al 2019, a monophyletic grouping was observed in Buaya et al (2019c) and Buaya and Thines (2020). Interestingly, the genus Ectrogella with its type species E. bacillariacearum, which was previously speculated to belong to the early-diverging lineages, was found to be embedded in the basal Saprolegniomycetes (Buaya and Thines 2020) and epitypified with a specimen exhibiting the typical thallus and exit-pore morphology described for the species by Zopf (1884).…”

“…Consequently, the olpidiopsis-like (i.e. those holocarpic oomycetes with simple thalli and zoospores that start swarming within the mature thallus) diatom parasitoids were assigned to a new genus, Diatomophthora, while the parasites of red algae were re-classified to the order Pontismales (Buaya et al 2019c;Buaya and Thines 2020), following the classification first suggested by Dick (2001).…”